This invention relates to lasers, and, more particularly, to lasers which emit in the deep red spectral region.
Many military systems would benefit from the development of sources of radiation which are "in band" to the receivers. For example, active optical target location systems require laser sources in the visible to near infrared region of the electromagnetic spectrum. This results from the fact that the return from an optical system (its cross section) is highest in its intended region of usage. Thus, for detection of visual or television optical systems sources in the spectral region from 0.4 to 0.9 micrometers are required.
Currently there are very few solid state laser sources under development which have the performance potential for these applications. Doubled Nd lasers which emit at 0.53 micrometers are inadequate for many applications because the radiation is visible to the naked eye. Er:LiYF.sub.4 which emits at 0.85 micrometers is unsatisfactory for certain applications because the wavelength is too far into the infrared. Ruby lasers which emit at 0.69 micrometers are basically three-level lasers with a high threshold which allows operation only at very low repetition rates.